1. Field of the Invention
The present invention relates to a two-way digital broadcasting system composed of a server apparatus that stores data and a data reception terminal apparatus that requests data transmission and performs data reproduction, where the apparatuses are connected by a network.
2. Description of the Prior Art
FIG. 1 is a representation of a conventional two-way digital broadcasting system. As shown in FIG. 1, a conventional two-way digital broadcasting system is composed of a server apparatus A that stores objects that are made up of data, such as video data and audio data, and control instructions, a plurality of data reception terminals B which request the transmission of objects from the server apparatus A and receive such transmission, and a network C that connects the server apparatus A to the data reception terminals B. Here, it is normal for the server apparatus A and each data reception terminal B to be connected by one data channel for transmitting a single data stream on the network C and one control channel for transmitting control information on the network C.
The following is a simplified explanation of the operation of the conventional two-way digital broadcasting system described above. First, a transmission request for an object is sent from a data reception terminal B to the server apparatus A via the control channel of the network C. In this specification, an xe2x80x9cobject xe2x80x9d refers to a collection of data in order to fulfill a specific function or purpose, and has a wide definition that includes control instructions as one type of data. On receiving the transmission request, the server A searches for the requested object and on finding it sends the corresponding data to the data terminal apparatus B via a data channel of the network C. This operation is repeated whenever new data is requested by the data reception terminal B. These object transmission requests for objects are issued by a data reception terminal B in accordance with indications from the user and control instructions included in received objects.
In the conventional two-way digital broadcasting system described above, the object whose transmission is requested is an object which is required immediately, so that the data reception terminal is unable to commence the following process from the time the transmission request is issued until the time the requested object is received. When the data reception terminal requests the transmission of new data, time is needed for the server A to search for the requested object before transmission, so that there are many cases where the data reception terminal has to wait a considerable amount of time before the new data arrives, which can be frustrating for users.
Depending on the content of the received data, there are cases where the data which will be requested next can be predicted with a high probability. Accordingly, to eliminate the waiting time required for the next data to arrive, ti would be possible for the data reception terminal to issue a transmission request beforehand for the predicted next set of data and then receive the data, enabling the data reception terminal to display the received data instantly where required.
However, in a two-way digital broadcasting system, it is normal for a server apparatus to transmit data to a data reception terminal on a data channel which is a single stream, so that if the preloading of a next set of data is performed unrestrictedly, there is the risk of interrupting the transmission of the data which is currently necessary. There are also problems such as that data will still be preloaded even when it becomes clear after requesting the transmissions of the data that the data is no longer necessary.
Since data is transmitted on a data channel that is a single stream, conventional systems have had a problem that when data, such as video data or audio data, whose transmission requires a significant amount of time is presently being transmitted and a transmission request is given for a next set of data, this data will not be transmitted until the transmission of the present data is completed, so that the data reception terminal will not be able to obtain the next data quickly in spite of the need to do so.
When it is known beforehand that a given object needs to be transmitted together with another object, it is conventional for the two objects to be combined into a large object which is then stored in the server and transmitted on request, or alternatively for a separate transmission request to be issued and executed for each of the two objects. With the former method, there is the problem that when the other object for a given object itself needs to transmitted together with yet another object, it becomes necessary to further combine this object and store the resulting file in the server. This leads to wasteful use of the storage capacity of the server and makes the management necessary when amending and adding objects extremely complex. On the other hand, with the latter method, while the storage capacity is not put to waste, it becomes necessary to execute two transmission requests, which increases the time taken by the transmission of objects.
The present invention was conceived in view of the stated problems, and has an object of reducing the time taken by data reception in response to an object transmission request in a two-way digital broadcasting system and of appropriately managing transmission requests and the present reception status.
The stated objects can be achieved by performing the procedure described below in a system with the following construction. A server apparatus stores a plurality of objects including at least one object that contains data and one object that contains a synchronous transmission request for issuing a transmission request for an object that is presently required and an asynchronous transmission request for issuing a transmission request for an object that has a high probability of becoming necessary in the future. The server apparatus is sent a transmission request for an object via a control channel of a network and sends the requested object via the data channel of the network.
In the procedure of the present invention, an object including control instructions that can be a synchronous transmission request or an asynchronous transmission request is received from the server apparatus. A control instruction in the received object is decoded, and it is judged whether a synchronous transmission request or an asynchronous transmission request is to be executed. When a synchronous transmission request is to be executed, a transmission request for an object is issued and decoding of a next instruction is not performed until the requested object has been received. On the other hand, when an asynchronous transmission request is to be executed, a transmission request for an object is issued and decoding of a next instruction is performed regardless of whether the request object has been received or not.
By performing the procedure described above, objects which are presently required will definitely be received and processed, while objects with a high probability of being required in the future will also be obtained in advance, so that when such objects become necessary in the future, the system will be able to instantly process the objects. Here, there is the additional effect of the asynchronous transmission requests not interrupting the other processes.
It is desirable for the procedure to be performed as described below when an object in the plurality of objects includes at least one of video data and audio data.
First, it is judged whether an object received by the object receiving unit includes vide data/audio data or other data, with video data being outputted to a video/audio reproduction unit and other data being outputted to a data storage unit.
By handling video/audio data and other data in this way, the different control methods for transmission requests can be used depending on whether video/audio data whose reception time is considerable is being received, on whether an object that contains video/audio data is to be transmitted or on whether an object that contains other data is to be transmitted. By doing so, more flexible transmission requests can be used, resulting in a more flexible reproduction process for objects.
In more detail, when a control instruction or a user indication is decoded and a synchronous transmission request is to be executed while video data or audio data is being outputted, a transmission termination request for the present object is first transmitted to the server apparatus.
With the above operation, when the data channel of the network is busy due to the transfer of video data or audio data, the transmission of the object that includes this video data or audio data is terminated, so that the reception of the object indicated by the synchronous transmission request which is presently required can be quickly performed, reducing the time taken by the processing as a whole.
When a control instruction or a user indication is decoded and an asynchronous transmission request is to be executed while video data or audio data is being outputted, the asynchronous transmission request is not performed.
By doing so, the reception of the video/audio data that is presently being reproduced is given priority and continued, while the asynchronous transmission request for the object that is likely to be needed in the future is not executed, thereby avoiding any interruptions to the reproduction of the video/audio data which would frustrate the user.
When an asynchronous transmission request has been issued for an object but the requested object has not yet arrived and, on decoding a user indication or a control instruction, a transmission request should be issued for an object including at least one of video data and audio data, a transmission termination request is first issued for the requested object of the asynchronous transmission request.
By doing so, the transmission of the object of the asynchronous transmission request which is not presently required is canceled and the object containing the video data or audio data that is presently required is received instead, meaning that the transmission of presently required objects is not interrupted by the transmission of objects which are not presently required.
When a first asynchronous transmission request has been issued for an object but the requested object has not yet arrived and, on decoding one of a user indication and a control instruction, a second asynchronous transmission request should be issued, a transmission termination request is first issued to the server apparatus for the requested object of the first asynchronous transmission request.
By doing so, the reception of an object that is likely to be needed in the future due to a latest asynchronous transmission request is not delayed by the transmission of an object requested by a preceding asynchronous transmission request.
When an asynchronous transmission request for an object has been issued to the server apparatus but a requested object has not yet arrived and, on decoding one of a user indication and a control instruction, a transmission request should be issued for an object that includes at least one of video data and audio data, the transmission request is not issued to the server apparatus until the requested object of the asynchronous transmission request has arrived.
By doing so, the object of the asynchronous transmission request can be received before the data channel becomes busy with the transfer of the video data or audio data whose reception time is very long.
It is also possible for objects to be received via the control channel of the network, so that when video data or audio data is being outputted and a transmission request for an object is issued, the object requested by the transmission request can be received via the control channel of the network.
By doing so, when the data channel is busy with the transfer of the video data or audio data, objects can be received via the control channel of the network.
The stated object of the present invention can be achieved by a server apparatus connected via network to a data reception terminal. This server apparatus stores a plurality of objects and when the server apparatus is transmitting video data and audio data to the data reception terminal apparatus and the data reception terminal apparatus gives issues a transmission request for an object, the server apparatus sends the object requested by the transmission request to the data reception terminal apparatus via the control channel of the network.
By doing so, when the data channel is busy with the transmission of video data or audio data to the data reception terminal apparatus, an object requested by a transmission request can be transmitted to the data reception terminal apparatus using the control channel.
The server apparatus of the present apparatus is also such that an object that includes list information showing other objects that are to be simultaneously transmitted with the object can also be stored in the server apparatus. When there is a transmission request for an object that includes list information, the server apparatus searches for the other objects given in the list information and also transmits these objects to the data reception terminal apparatus.
By doing so, there is no need to combine objects that are simultaneously necessary into large files, and a same file can be indicated in the list information of multiple objects, so that improvements are made in the efficiency of the use of the data storage unit of the server apparatus. There is also no need to use a plurality of transmission requests for a plurality of objects, increasing the speed at which the requested objects can be transmitted.